This is an application for the K99/R00 Pathway to Independence Award for Dr. Chunyue Yin, a post- doctoral fellow at the University of California, San Francisco. Dr. Yin is establishing herself as a young investi- gator in the research of alcoholic liver disease (ALD). This K99/R00 award will provide Dr. Yin with the support necessary to accomplish the following goals: 1) to gain expertise in hepatic stellate cells (HSC) and alcoholic liver injury; 2) to develop new tools for studying HSC in zebrafish; and 3) to develop an independent research career. To achieve these goals, Dr. Yin has assembled a mentoring team comprised of a primary mentor, Dr. Didier Stainier, Professor of Biochemistry and Biophysics at UCSF, who is an expert in zebrafish liver development, and a co-mentor, Dr. Jacquelyn Maher, Professor of Medicine at UCSF, who is an expert in al- coholic liver injury. ALD is one of the leading causes of alcohol-related morbidity and mortality. Activation of HSC is the key event in ALD, but our understanding of the regulation of HSC in alcoholic liver injury is limited. Dr. Yin's long-term goal is to elucidate the cellular responses of HSC in alcoholic liver injury. The overall objective of this application is to understand the interactions between HSC and neighboring sinusoidal endothelial cells (SEC) in liver development and acute alcoholic injury by using the zebrafish model. The central hypothesis is that paracrine signals between HSC and SEC are required for HSC development and regulate their behaviors in response to alcohol. Dr. Yin will achieve the objective of the proposal by pursuing three specific aims: 1) Understand the roles of SEC in HSC development; 2) Determine the responses of HSC and SEC to acute al- coholic liver injury; and 3) Understand the molecular basis of HSC-SEC interactions in response to acute alco- holic liver injury. In Aim 1, she hypothesizes that in zebrafish HSC and SEC do not share a common precur- sor, yet SEC are essential for HSC development. She will test this hypothesis by lineage-tracing experiments and by manipulating the interactions between HSC and SEC during development. In Aim 2, Dr. Yin will char- acterize the cellular responses of HSC and SEC to acute alcohol exposure by time-lapse live imaging experi- ments. In Aim 3, she will perform gene-profiling analyses to characterize the molecular mechanisms underly- ing the responses of HSC and SEC to acute alcohol treatment. She will also test the role of Platelet-Derived Growth Factor in regulating HSC-SEC interactions. The proposed research is innovative because it estab- lishes a novel zebrafish model for studying HSC-SEC interactions in alcoholic liver injury. The proposed re- search is also significant because it is the first step in a continuum of research that is expected to elucidate the mechanisms of HSC activation in alcoholic liver injury. The rationale for the proposed research is that a com- prehensive characterization of HSC in development and acute alcohol exposure will provide novel insights into our understanding of HSC in ALD, and may translate into new targets for therapy.